[Amps] Plate Choke Resonances

Carl km1h at jeremy.mv.com
Sun Jan 31 09:12:05 PST 2010


By various methods over the decades, out of circuit, and the open and short 
procedure. Loosely coupled GDO, spectrum analyzer, and VNA. Note that in the 
cases where Ive had all 3 methods available at the same time there is close 
agreement.

Carl
KM1H

----- Original Message ----- 
From: "Gary Schafer" <garyschafer at comcast.net>
To: "'Carl'" <km1h at jeremy.mv.com>; <dezrat1242 at yahoo.com>; "'Amps 
reflector'" <amps at contesting.com>
Sent: Sunday, January 31, 2010 11:54 AM
Subject: RE: [Amps] Plate Choke Resonances


> Carl,
>
> How did you measure the parallel resonance of the choke?
> How did you determine the difference between parallel resonance and series
> resonance?
>
> 73
> Gary  K4FMX
>
>> -----Original Message-----
>> From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com]
>> On Behalf Of Carl
>> Sent: Sunday, January 31, 2010 9:22 AM
>> To: dezrat1242 at yahoo.com; Amps reflector
>> Subject: Re: [Amps] Plate Choke Resonances
>>
>>
>> ----- Original Message -----
>> From: "Bill, W6WRT" <dezrat1242 at yahoo.com>
>> To: "Amps reflector" <amps at contesting.com>
>> Sent: Sunday, January 31, 2010 1:43 AM
>> Subject: Re: [Amps] Plate Choke Resonances
>>
>>
>> > ORIGINAL MESSAGE:
>> >
>> > On Sat, 30 Jan 2010 22:27:47 -0700, Larry Benko <xxw0qe at comcast.net>
>> > wrote:
>> >
>> >>
>> >>I just ran a simulation with a tube with a 3000 ohm impedance and
>> 3000V
>> >>peak AC on the plate connected to a 100uH plate choke at 10MHz.
>> >
>> > REPLY:
>> >
>> > The problem with your simulation is that the voltage is held to a
>> > constant 3000 V. In the real world the "Tesla effect" will cause the
>> > voltage to rise far higher and that is what causes the smoke.
>> >
>> > One real world experiment is worth a thousand simulations, IMO.  :-)
>> >
>> > 73, Bill W6WRT
>> >
>>
>> Ive made it a point over the years to test any plate choke I could get
>> my
>> hands on and build those in magazine or Internet articles.
>>
>> Almost without fail the ones using larger than necessary diameter wire
>> show
>> a pronounced parallel resonance in or very close to a ham band. This
>> makes
>> me think that the builder went the brute force method to avoid smoke
>> since
>> #22 or 24 isnt needed at 1200-1500W which is what levels they were used
>> in.
>>
>> Probably the simplest and cleanest 160-10M choke is the old Amp Supply
>> version used in all their amps with real transmitting tubes. One size
>> fits
>> all. Tests in the 5KW+ LK-800C and other versions with the 3500V tap and
>> three 3CPX800A7's show absolutely no heating problems on any band. This
>> 90uh
>> choke has 2 1/8" of #26 on an unglazed 3/4" ceramic form, more properly
>> referred to as technical ceramic. Im no chemist but Ive been told that
>> the
>> porcelain glazed contain some amounts of metal??
>>
>> Anyway, the series resonances are 12.8 and 49mHz and the parallel ones
>> are
>> 13.0 and 27.2 mHz. A .001 and .01 uF bypass keeps any pesky RF out of
>> the
>> electrolytics and wiring. Naturally, on 160M the tank circuit is
>> involved as
>> part of the choke circuit as already mentioned on here many times over
>> the
>> years.
>>
>> Maybe I havent been involved with sufficient voltages and power, Ive
>> stopped
>> at 10KW in my commercial life,  but Ive yet to see a Tesla effect from a
>> plate choke. Many times in the bandswitch or Tune cap for other reasons
>> but
>> nothing to do with choke resonances.
>>
>> Perhaps the closest Ive been to ham amp choke fireworks is the various
>> Dentrons when run on 12M. Remove 4 turns from the top and all is well.
>> The
>> 1st generation Ameritrons used to do a nice display also when WARC was
>> opened. While they were still figuring out a new design I simply
>> installed a
>> B&W 802 in order to get customers back on the air ASAP.
>>
>> Carl
>> KM1H
>>
>>
>>
>>
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